There is a need for alternative polymer technologies that are compatible with existing epoxy resin process flows for semiconductor and semiconductor packaging. Ring-Opening Metathesis Polymerization (ROMP) is a well-known mode of polymerization that can form useful thermoplastic and thermoset materials for a variety of semiconductor applications. The materials can be wholly hydrocarbon or can contain polar functional groups, and the cure rate can be very rapid. The dielectric constant is intrinsically low for many of these materials, allowing compatible integration into other low-k processes. ROMP is promoted by transition metal catalysts. These catalysts have historically been air, moisture, and temperature sensitive, which limits the polymerization processes to those that are amenable to air and moisture free conditions or to processes in which the polymerization occurs at a rate greater than the rate of decomposition of the catalyst.
Additionally, the rate of ROMP at room temperature with commonly used catalysts is quite rapid for strained cyclic olefins, which prevents formulation of one-part mixtures of cyclic olefin monomers and metathesis catalysts. ROMP of dicyclopentadiene (DCPD, C10H12), for example, forms a rigid crosslinked polymer when polymerized, but the rate of reaction is so fast that mixtures of dicyclopentadiene and metathesis catalysts are not stable; polymerization of DCPD would spontaneously occur for most metathesis catalysts. This aspect of the current art prevents the preparation of curable mixtures of strained cyclic olefins and metathesis catalysts for use most processes related to electronics packaging.
The sensitivity of metathesis catalysts and the rapid rate of ROMP of strained cyclic olefins at room temperature require handling and processing procedures that are amenable to very rapid polymerization and cure and that keep the monomer separated from the catalyst until just prior to the polymerization. DCPD, for example, is most often polymerized and processed into parts via reaction injection molding (RIM) or resin transfer molding (RTM). Typically a solution of precatalyst in liquid DCPD is mixed with a solution of catalyst activator in DCPD, which initiates the polymerization. The mixture is then pumped into a mold where the polymerization continues to form the final cross-linked part.